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Earth's Structure/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby A boy, Tim, reads from a typed letter. TIM: Dear Tim and Moby, What's the earth made of, anyway? From K.L. Heley. A robot, Moby, stands by Tim. Moby hits his own body, making a tinny, hollow sound. TIM: Well, there is a lot of metal in the earth, along with silicon-based rock. MOBY: Beep. An animation shows a city skyline shaking back and forth. TIM: How do we know? Earthquakes. An animation shows the interior of the Earth. Wavy arrows move across the various layers. TIM: Like any other waves, earthquake waves bend when they travel through different materials. By studying the way earthquakes vibrate through the interior of the planet, scientists have been able to get a pretty good idea of earth's internal structure. MOBY: Beep. Moby finds a big globe and slices it in the middle with a knife. TIM: Yikes. An image shows a diagram of the inside of the earth. The earth’s layers are represented by a yellow circle in the middle, a small orange circle around it, and a much larger orange circle around that circle. A smaller olive circle is around the large orange circle. TIM: The earth has three basic layers: the core, the mantle, and the crust. An image shows a landscape, water, sky, and the sun. TIM: The crust is the part of the earth we live on. We can only see the very top layer of the crust. Underneath all that grass and dirt and sand and water and stuff, is a layer of hard rock. An image shows the crust area with measurements of 35-70 kilometers (km) for land and 5-10 km for a body of water with a much larger area beneath it. TIM: The crust is about five to ten kilometers thick in the ocean basins and thirty-five to seventy kilometers thick in the continents. Below the crust you'll find the mantle. An image shows a part of the inside of the earth's diagram. Rotation arrows are shown to represent heat. TIM: The mantle is made up of a mixture of elements including silicon, iron, magnesium, and oxygen. It goes down from the bottom of the crust to about 2900 kilometers deep, and heat churns through it. The mantle makes up the bulk of the earth's mass, about two-thirds of it in fact. Parts of the upper mantle are soft and plastic. This is what allows the tectonic plates that make up the earth's surface to move around. The lower mantle is solid, and extremely hot. At the very center of the earth, you'll find the core. An image of the core has colored circles that show the different chemical composition of each layer. TIM: The outer core is earth's only totally liquid layer. It's about 2300 kilometers thick and made of molten iron and nickel. The pressure from all those layers pushing down creates a solid ball in the very center of earth, called the inner core. It's made of mostly iron, and it could be found somewhere around 5100 kilometers below the surface. An animation shows the layers with arrows indicating movement of the inner core around the outer core and how it spins. TIM: The inner core floats in the outer core and spins at a different rate than the rest of the planet. An image shows the earth with waves emanating from it. TIM: This, along with the convection currents in the mantle, is probably what causes earth's magnetic field. MOBY: Beep. TIM: Well, nobody knows this stuff for sure. An image shows the crust of the earth. An arrow points to a small indent in the crust. TIM: The deepest hole ever drilled was only about twelve kilometers deep. The image then reveals how small that indent is by showing the rest of the interior of the earth. TIM: That's only a tiny fraction of the 6355 kilometers to the center of the earth. Moby starts to dig with a shovel in a field. MOBY: Beep. TIM: OK, but I'm telling you, it's going to take a long time to get to the core. Tim scratches his head. TIM: Ah, I'll call you when dinner's ready. Category:BrainPOP Transcripts